(a) Field of the Invention
The present invention relates to an improved spacer, and more particularly to a composite profile shaped spacer for use in compressed gas insulated coaxial electrical cables to support a central conductor substantially concentric with an outer envelope conductor and wherein the spacer has substantially uniform field distribution and low field intensity on the opposed surfaces thereof.
(b) Description of Prior Art
With the rapid development of compressed gas insulated (CGI) cables and switchgear in recent years, underground transmission at EHV levels of 500 kV and above is becoming one of the alternatives to the problem of supplying energy to large urban areas. Several factors have been observed to affect the dielectric performance of the CGI cable. These factors are the electrode surface condition, the particle contamination and the presence of dielectric spacers. The latter aspect is of particular importance since solid-dielectric spacers are an integral part of the cable, and as such, they should be properly designed to minimize the degradation in the dielectric performance of the cable.
Several studies have been made on EHV cables with compressed SF.sub.6 insulation, in the last few years. Field calculations are extensively used in these studies. The optimization criteria vary, however, considerably from these studies. The results obtained are, therefore, far from sufficient to establish a universal configuration for epoxy spacers as illustrated by the large variety of epoxy spacer configurations in commercial use.